Traditional fluorescent tube lamps, such as for example T-5 and T-8 lamps, use fluorescent technology and only require two pins, e.g., electrical contacts, at the two ends of the tube lamp and in corresponding contacts in the lampholders. These lampholders, typically referred to as tombstone style lampholders are generally well known in the art.
For example, U.S. Pat. No. 2,247,117 describes a lampholder or socket for a lamp having a double end discharge, such as a fluorescent tube design. The described socket includes a base, a cover, and two contact members. The contact members cooperate with and engage the contact pins extending from a base at each end of the tubular lamp, such as a fluorescent lamp. The base and housing of the socket are typically made of any suitable insulating material. In use, the contacts of the tubular lamp are mounted to the socket by inserting the contacts of the lamp into a slot provided in the socket. Thereafter, the lamp is rotated ninety degrees to engage the contacts of the lamp with the contacts of the lampholder.
Recently, new light-emitting diode (LED) tubes have been designed to fit into the same lampholders as previously used in fluorescent tube lamps. An LED tube is made up of dozens of individual LEDs. They come in a variety of sizes (e.g., 2, 4 or 6 feet), different color temperatures (i.e., different colors of light), and varying lumen output. LED tubes can be purchased with new fixtures, or used for retrofitting existing fixtures. However, LED tubes don't require the ballasts that traditional fluorescents need, so the ballasts need to be removed when replacing fluorescent bulbs with LED tubes. Instead of a ballast, LEDs use a driver to convert the line AC voltage to DC and to provide other conditioning and control. Often the driver is contained in the same housing as the LEDs, meaning a line voltage shock risk is present Other times, even with the driver housed separately, the input DC voltage to the lamp can still be high enough to be a shock risk (NEC Circuit Class 1). As such, LED lamps can sometimes pose a safety risk due to exposed metal for reasons such as, for instance, heat-sinking or electrical contacts.
Recently some LED systems have been developed with switches in the LED tubes for safety purposes. These safety switches, while sufficient for their intended purposes, add cost and complexity to the lamp that may not be desirable in some manufacturing instances.
Still further, in other LED tube systems, such as the Japanese JELMA 801 standard, an incorporated ground path is provided for performance reasons. For instance, a GX16t-5 LED lamp includes a power input side, having two connectors, and a ground side at the opposite end. In operation, the user can insert the power side into the respective lampholder before inserting the ground side. Oftentimes, insertion of the power side first is without risk to the installer, but that may not always be the case, such as for instance, when the power level is not NEC Circuit Class 2.
Thus, there is a recognizable need for safe and convenient methods and apparatus for grounding an LED tube as disclosed herein.